Great. Someone introduced Ansible Playbook like this

Keywords: Linux Operation & Maintenance CentOS architecture cloud computing

Great! Someone introduced Ansible Playbook like this!

After a series of basic training and honing, it finally came to the application of relatively tall.

(Nani is just starting to review his future:

1. What is playbook

Chinese Name: script, which is an automatic processing script. Playbook is written in YAML language.

2. playbook demo

The following is a simple operation demonstration. Write the host list before writing the script.

(so, the foundation is very important. If you don't remember the host list And configuration files How to use it, learn it quickly.)

[student@servera ~]$ cat hosts 

[student@servera ~]$ cat webserver.yml 
- name: play to setup web server
  hosts: servera
  remote_user: root
  become: yes
  become_method: sudo
  - name: latest httpd version install
      name: httpd
      state: latest

[student@servera ~]$ ansible-playbook -i hosts webserver.yml 
PLAY [play to setup web server] *********************************************************

TASK [Gathering Facts] ******************************************************************
ok: [servera]

TASK [latest httpd version install]******************************************************
changed: [servera]

PLAY RECAP ******************************************************************************
servera                    : ok=2    changed=1    unreachable=0    failed=0

3. Playbook workflow

  • A playbook script is a list of one or more "plays"
  • The main function of play is to dress up a predefined group of hosts as roles defined in advance through the task in ansible
    In fact, it calls a module of ansible to organize multiple plays in a playbook, that is, they can be combined
    To perform predefined actions according to a pre choreographed mechanism.
  • Playbook files are written in YAML language

(just like the picture comic book, scripts are "scripts" written by us according to specific needs. This "script" uses various modules to meet the needs by acting on a specific host list.)

4. Introduction to yaml syntax

Only the playbook related syntax is involved here (please refer to the official website for more information) ).

The grammar is very strict. Please be careful.

In a single file, three consecutive hyphens can be used(---)Distinguish multiple files. In addition, there are optional three consecutive periods( ... )Used to indicate the end of a file
 The next line starts writing normally Playbook It is generally recommended to specify the content of the Playbook Function of
• use#No. comment code
• Indents must be uniform, not spaces and tab Mixed use,Generally indent 2 spaces (can be modified) tab (indent as)
• The indent level must also be consistent. The same indent represents the same level. The program determines the level of configuration by indenting and line feed
• YAML Document content and Linux The case judgment method of the system is consistent, which is case sensitive, key/value All values must be case sensitive
• key/value The value of can be written on the same line or wrapped. The same line is used , Comma separated
• value It can be a string or another list
• A complete code block function needs to include at least one element name and task
• One name Only one can be included task
• use | and > To separate multiple lines, which is actually just one line.
        include_newlines: |
            exactly as you see
            will appear these three
            lines of poetry

        ignore_newlines: >
            this is really a
            single line of text
            despite appearances
• Yaml Escape symbols are not allowed in double quotation marks, so single quotation marks are used to avoid escape symbol errors 
• YAML The file extension is usually yml or yaml

Many students who have just learned often hang on the grammar when they report an error. They can understand it through continuous practice.

(the basis of grammar is really important. Stop talking, you don't listen, you don't understand, you don't do when you understand, you make mistakes when you do, you don't recognize when you're wrong, you don't change when you recognize you, and you don't accept when you change.)

List: List

All its elements begin with "-"

- web
- dns
-Space web        # Writing format

Dictionary: Dictionary (key value pair)

It usually consists of multiple key s and value s

Multiline writing:
name: hunk
blog: "xxxxx"
name:Space hunk   > This colon must be followed by a space

Same line:
Need to use{ }
{name: hunk, blog: "xxxxxx"}  > It is recommended to leave a space after the comma

Representation of Boolean values:
yes/no  true/false

create_key: yes
needs_agent: no
knows_oop: True
likes_emacs: TRUE
uses_cvs: false

5. Playbook core elements


Optional configuration item, which can help record the operation instructions of playbook.


The contents of the hosts line are the patterns of one or more groups or hosts, separated by commas. It is usually a list of hosts defined by / etc/ansible/hosts

remote_user is the account name for remote task execution:

- hosts: web,dns
  remote_user: root


Task set

    - name: install httpd
      name: httpd

    - name: start httpd
      service: name=httpd state=started

6. Transform the tab function in vi

In order to edit the playbook more easily, you can set that when vi edits yaml files, pressing tab will make a double space indent.

Add the following to $HOME/.vimrc

autocmd FileType yaml setlocal ai ts=2 sw=2 et

Parameter interpretation:

set ai    # Auto indent
set ts=2  # tabstop means that after pressing a tab, the displayed is equivalent to several spaces. The default is 8.
set sw=2  # shiftwidth, indicating the indented length of each level
set et    # expandtab, convert the tab into a space, and the indentation is represented by a space

(don't ask me why I want to rewrite it, because when you see others clattering their keyboards and writing playbook, you may still silently recite how many spaces you pressed. >. <)

7. playbook writing style

In the following writing examples, the shorthand format is an old writing method:

- name: copy new yum config to host
  copy: src=/etc/yum.repos.d/ dest=/etc/yum.repos.d/

Universal yaml format:

- name: copy new yum config to host
    src: /etc/yum.repos.d/ 
    dest: /etc/yum.repos.d/

Basically, new writing methods are used to facilitate reading and troubleshooting.

8. playbook execution

Detection syntax: ansible playbook -- syntax check webserver.yml

Simulation execution: ansible playbook - C webserver.yml

Real execution: ansible playbook webserver.yml

Level of detail of execution:
-v   : Displays the task results.
-vv  : The task results and task configuration are displayed
-vvv : Contains information about connecting to the managed host
-vvvv: Added additional detail level options related to the connection plug-in, including the user used to execute the script on the managed host and the script executed

9. Practice demonstration - how to write playbook

Set tab indent

[student@servera ~]$ cat .vimrc 
autocmd FileType yaml setlocal ai ts=2 sw=2 et

View configuration file and host list

[student@servera ~]$ mkdir playbook

[student@servera playbook]$ cat ansible.cfg 


[student@servera playbook]$ cat inventory 

Write the required script

[student@servera playbook]$ cat site.yml 
- name: Install and start Aapche HTTPD
  hosts: web
    - name: httpd package is present
        name: httpd
        state: present

    - name: correct index.html is present
        content: "This is a test page.\n"
        dest: /var/www/html/index.html

    - name: httpd is started
        name: httpd
        state: started
        enabled: true

Syntax check

[student@servera playbook]$ ansible-playbook --syntax-check site.yml 

playbook: site.yml

It is a good habit to check the grammar before running the script.

Execute script

[student@servera playbook]$ ansible-playbook site.yml
PLAY [Install and start Aapche HTTPD] ***************************************************
TASK [Gathering Facts] ******************************************************************
ok: [serverc]
ok: [serverd]

TASK [httpd package is present] *********************************************************
changed: [serverd]
changed: [serverc]

TASK [correct index.html is present] ****************************************************
changed: [serverc]
changed: [serverd]

TASK [httpd is started] *****************************************************************
changed: [serverc]
changed: [serverd]

PLAY RECAP ******************************************************************************
serverc    : ok=4    changed=3    unreachable=0    failed=0   
serverd    : ok=4    changed=3    unreachable=0    failed=0


[student@servera playbook]$ ansible-playbook site.yml

This is one of the important features of Ansible, which is easier to understand with practice demonstration.

Result access check

[student@servera playbook]$ curl serverc
This is a test page.
[student@servera playbook]$ curl serverd
This is a test page.

10. playbook rights

It can be written in the script at the same level as hosts and tasks

- hosts: all
  become: true
  become_method: sudo
  become_user: root
  - debug:
     msg: "Test"

Of course, it's OK not to write in the script, but in the configuration file. If you write in both places, the priority in the script will be higher than that in the configuration file. For example, when the authorization is started in the configuration file, become: yes, but become: no is configured in the script, which will eventually take effect as the configuration in the script.

11. Module documentation

Ansible doc - L view list

Ansible doc modulenamiew the module help file

(summary of the previous article) Mentioned, it's really important to check the help ~ ~)

12. Practice demonstration - execute multiple playbook s

View configuration file and host list

[student@servera ~]$ mkdir playbook-multi
[student@servera ~]$ cd playbook-multi/
[student@servera playbook-multi]$ cat ansible.cfg 


[student@servera playbook-multi]$ cat inventory 

Write the required script

[student@servera playbook-multi]$ cat web.yml 
- name: Enable web services
  hosts: servera
  become: yes
    - name: latest version of httpd and firewalld installed
          - httpd
          - firewalld
        state: latest

    - name: test html page is installed
        content: "Hello World!\n"
        dest: /var/www/html/index.html

    - name: firewalld enabled and running
        name: firewalld
        enabled: true
        state: started

    - name: firewalld permits http service
        service: http
        permanent: true
        state: enabled
        immediate: yes

    - name: httpd enabled and running
        name: httpd
        enabled: true
        state: started

- name: Test web server
  hosts: localhost
  become: no
    - name: connect to web server
        url: http://servera
        return_content: yes
        status_code: 200

Syntax check

[student@servera playbook-multi]$ ansible-playbook --syntax-check web.yml 

playbook: web.yml

Use - v to execute the script

[student@servera playbook-multi]$ ansible-playbook web.yml -v
PLAY [Enable web services] **************************************************************

TASK [Gathering Facts] ******************************************************************
ok: [servera]

TASK [latest version of httpd and firewalld installed] ******************************************
ok: [servera] => {"changed": false, "msg": "", "rc": 0, "results": ["All packages providing httpd are up to date", "All packages providing firewalld are up to date", ""]}

TASK [connect to web server] ************************************************************
ok: [localhost] => {"accept_ranges": "bytes", "changed": false, "connection": "close", "content": "Hello World!\n", "content_length": "37", "content_type": "text/html; charset=UTF-8", "cookies": {}, "cookies_string": "", "date": "Fri, 04 Sep 2020 12:54:49 GMT", "etag": "\"25-5ae7c5e78c9df\"", "last_modified": "Fri, 04 Sep 2020 12:54:27 GMT", "msg": "OK (37 bytes)", "redirected": false, "server": "Apache/2.4.6 (Red Hat Enterprise Linux)", "status": 200, "url": "http://servera"}

PLAY RECAP **********************************************************************************
localhost                  : ok=2    changed=0    unreachable=0    failed=0   
servera    : ok=6    changed=0    unreachable=0    failed=0


  • yaml syntax is very strict and written carefully.
  • Modify the tab key to improve the efficiency of script writing.
  • Grammar checking is a good habit.
  • Make good use of module documents to view parameter descriptions and examples.
  • Understand idempotency through practice and experiment.
  • You can use the - v parameter to view the detailed output for troubleshooting.
  • If you like brother goldfish's article, you can like it easily. You can also pay attention to it, because you will continue to get dry goods in the follow-up.

Posted by Sassy34 on Sun, 05 Dec 2021 07:39:37 -0800